The invention relates to a process for the selective and quantitative elimination of lactoglobulins from a starting material containing whey proteins.
Dietary milk-based foods for infants are often manufactured from proteins extracted from cow's milk. In order to resemble human milk, a special formulation of the different ingredients of cow's milk is necessary and, exclusively from the standpoint of the proteins, it must be ensured that the aminogram (and especially the provision of essential amino acids such as threonine, tryptophan and lysine) is as close as possible to that of the proteins of human milk.
For this purpose, it is necessary, in particular, to shift the balance of the whey proteins/caseins ratio of cow's milk in favour of the whey proteins. The dietary milk-based feeds thereby obtained contain a high proportion of whey proteins. The following problem then arises: the protein fractions of human and bovine wheys do not have the same compositions; in particular, human whey does not contain beta-lactoglobulin, whereas approximately half the protein fraction of bovine whey is represented by beta-lactoglobulin. This difference in composition is the source of allergic phenomena in some infants when the latter are fed with milks of composition based on serum proteins of bovine origin. This allergy is manifested, in particular, in digestive disorders (abdominal pain, diarrhea, vomiting).
Several proposals have been made for solving this problem, employing, for example, thermal denaturation of the proteins, total hydrolysis of the proteins to very short peptides or quantitative elimination of the lactoglobulins.
Thermal denaturation of the proteins considerably impairs their digestibility.
Total hydrolysis of the proteins leads to production of preparations which then contain only peptides and are free from residual proteins. This hydrolysis may be carried out either chemically (by means of acid or base) or enzymatically. In the case of enzymatic hydrolysis, it is often necessary to use several proteases of complementary specificities (for example trypsin, chymotrypsin, pepsin, papain, bacterial proteases) in order to achieve the desired degree of hydrolysis; the quantities of enzymes to be used are often large. Whether the hydrolysis is chemical or enzymatic, residual proteins which are not digested because they are particularly resistant to hydrolysis (especially serum albumin and immunoglobulins) often remain in the preparations. If the recovery of only peptides is desired, these proteins must be eliminated by an additional treatment (precipitation/centrifugation, ultrafiltration).
The elimination of lactoglobulins from wheys has already been the subject of several studies. For example, the elimination of the lactoglobulins may be undertaken by exploiting the fact that lactoglobulins are still soluble under conditions in which all the other major whey proteins are not. A process is thus proposed by KUWATA et al (1985) (in J. Food Sci, V.50, N. 3; pp 605-609: Elimination of beta-lactoglobulin from whey to simulate human milk protein): ferric chloride is added to the whey and the pH is adjusted to 3; all the proteins precipitate with the exception of the lactoglobulins, the precipitate is recovered and the ferric ions are then eliminated either by ion exchange chromatography or by ultrafiltration. The protein concentrate obtained does not contain lactoglobulins. This process has the drawback of impairing the digestibility of the proteins thus precipitated.
Another process, studied by CHIANCONE and GATTONI (EP-A-285,576) exploits the property possessed by lactoglobulins of associating to dimers under certain conditions: lactoglobulins are immobilized on a support, and the whey from which it is desired to extract the lactoglobulins are passed through this support; the lactoglobulins are eliminated selectively by association
the lactoglobulins of the support.
It may be noted that ion exchange resins of all types have already been used for the separation of whey proteins, but the object of the procedures adopted was separation of the collective proteins or enrichment in one type of protein, and these procedures could not lead to the selective extraction of lactoglobulins.
The following studies may be mentioned:
French Application for a Certificate of Addition No. 77/24,162 (Rhone-Poulenc):
Use in series of anion exchange resins and silicas to isolate the collective proteins of wheys.
French Patent No. 79/08,555 (BEL):
Use of one or more types of resins for separating the proteins of whey or obtaining fractions enriched in a particular protein. The procedure adopted comprise a special pretreatment and post-treatment of the starting material.